Relationship Between the Azimuthal Dependencies of Nuclear Modification Factor and Ridge Yield

TL;DR

This paper links the azimuthal dependence of nuclear modification factors and ridge yield in heavy-ion collisions, providing a unified framework that explains observed anisotropies through surface semihard scattering.

Contribution

It introduces a model connecting azimuthal anisotropy, ridge yield, and nuclear modification factors based on initial geometry and surface semihard scattering.

Findings

Reproduces v_2, R_{AA}, and ridge yield simultaneously

Provides a unified description of azimuthal dependencies in heavy-ion collisions

Highlights the role of surface semihard scattering in azimuthal anisotropy

Abstract

The azimuthal angular dependence of the nuclear modification factor R_{AA}(p_T, phi,N_{part}) recently obtained by PHENIX is related at low p_T to the trigger phi dependence of the ridge yield as measured by STAR in a framework in which the azimuthal anisotropy is driven by semihard scattering near the surface. Careful consideration of the initial geometry leads to the determination of a surface segment in which the production of semihard partons are responsible for the phi dependence of the inclusive distribution on the one hand, and for the angular correlation in ridge phenomenology on the other. With v_2 also being well reproduced along with R_{AA} and ridge yield, all relevant phi dependencies in heavy-ion collisions can now be understood in a unified description that emphasizes the ridge production whether or not a trigger is used.